Method and apparatus for x-ray microscopy

ABSTRACT

This disclosure presents systems for x-ray microscopy using an array of micro-beams having a micro- or nano-scale beam intensity profile to provide selective illumination of micro- or nano-scale regions of an object. An array detector is positioned such that each pixel of the detector only detects x-rays corresponding to a single micro- or nano-beam. This allows the signal arising from each x-ray detector pixel to be identified with the specific, limited micro- or nano-scale region illuminated, allowing sampled transmission image of the object at a micro- or nano-scale to be generated while using a detector with pixels having a larger size and scale. Detectors with higher quantum efficiency may therefore be used, since the lateral resolution is provided solely by the dimensions of the micro- or nano-beams. The micro- or nano-scale beams may be generated using an arrayed x-ray source or a set of Talbot interference fringes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Patent Application is a continuation-in-part of U.S. patentapplication Ser. No. 15/173,711, filed Jun. 5, 2016 and entitled “X-RAYTECHNIQUES USING STRUCTURED ILLUMINATION”, which claims the benefit ofU.S. Provisional Patent Application Nos. 62/171,377, filed on Jun. 5,2015 and entitled “X-RAY TECHNIQUES USING STRUCTURED ILLUMINATION”, and62/343,594, filed on May 31, 2016 and entitled “X-RAY MICRODIFFRACTIONWITH STRUCTURED ILLUMINATION FOR STRAIN MEASUREMENT IN NANOELECTRONICS”,all of which are incorporated herein by reference in their entirety.

Application Ser. No. 15/173,711 additionally is a continuation-in-partof U.S. patent application Ser. No. 14/712,917, filed May 15, 2015 andentitled “X-RAY METHOD FOR MEASUREMENT, CHARACTERIZATION, AND ANALYSISOF PERIODIC STRUCTURES”, which in turn is a continuation-in-part of U.S.patent application Ser. No. 14/700,137, filed Apr. 29, 2015 and entitled“X-RAY INTERFEROMETRIC IMAGING SYSTEM”, both of which are incorporatedherein by reference in their entirety.The present Application additionally claims the benefit of U.S.Provisional Patent Application Nos. 62/401,164, filed Sep. 28, 2016 andentitled “X-RAY MEASUREMENT TECHNIQUES USING MULTIPLE MICRO-BEAMS”,62/429,587, filed Dec. 2, 2016 and entitled “METHOD FOR TALBOT X-RAYMICROSCOPY”; 62/429,760, filed Dec. 3, 2016 and entitled “MATERIALMEASUREMENT TECHNIQUES USING MULTIPLE X-RAY MICRO-BEAMS”, and62/485,916, filed Apr. 15, 2017 and entitled “TALBOT X-RAY MICROSCOPE”,all of which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The embodiments of the invention disclosed herein relate to microscopysystems using x-rays, and, in particular, measurement, characterizationand analysis systems using a system of periodic micro-beams toilluminate an object to determine various structural and chemicalproperties of the object.

BACKGROUND OF THE INVENTION

Conventional x-ray microscopes that utilize imaging optics are generallylimited by the resolution of the x-ray optics (e.g. zone plates) and/orthe resolution of the pixel size of the detector. For projection-basedsystems, the resolution is limited by the size of the x-ray source andthe finite pixel size of the detector. Although some commercial x-raymicroscope systems utilizing zone plates have a resolution of less than100 nm, such systems have an extremely limited field of view. Projectionbased x-ray microscopes do provide reasonable field of view withresolution better than 1 micron, but the acquisition times forreasonable signal-to-noise ratio tend to be very long, rendering thetechnique practically useless for many applications. Therefore, x-raymicroscopy with resolution smaller than 1 micron while also having alarge field-of-view has difficulty producing images with an integrationtime short enough to make the technique practical.

There is therefore a need for high-resolution microscopy systems thatcan provide both high resolution and a large field of view.

BRIEF SUMMARY OF THE INVENTION

This disclosure presents systems for x-ray microscopy using an array ofmicro-beams having a micro- or nano-scale beam intensity profile toprovide selective illumination of micro- or nano-scale regions of anobject. An array detector is positioned such that each pixel of thedetector only detects x-rays corresponding to a single micro-beam,allowing the signal arising from the x-ray detector to be identifiedwith the specific, limited micro- or nano-scale regions illuminated.Sampled transmission images of the object under examination at a micron-or nano-scale can therefore be generated while using a detector withpixels having a larger size and scale.

In some embodiments, the micro- or nano-scale beams may be provided byproducing a set of Talbot interference fringes, which can create a setof fine x-ray micro-beams propagating in space. In some embodiments, thearray of micro- or nano-beams may be provided by a conventional x-raysource and an array of x-ray imaging elements (e.g. x-ray lenses).

In some embodiments, both the detector and the object are placed withinthe same defined “depth-of-focus” (DOF) range of a set of Talbotanti-nodes. In some embodiments, the object is positioned on a mountthat allows translation in the x- and y-directions perpendicular to thedirection of x-ray beam propagation, allowing a “scanned” transmissionimage on a microscopic scale to be assembled. In some embodiments, theobject is positioned on a mount that allows rotation about an axis at apredetermined angle to the direction of x-ray beam propagation, allowingthe collection of data on a microscopic scale to be used forlaminographic or tomographic image reconstruction.

In some embodiments, additional masking layers may be inserted in thebeam path to block a selected number of the micro-beams, allowing theuse of less expensive detectors with larger pixel sizes for theremaining micro-beams. In some embodiments, the use of a masking layeralso allows the use of a detector with enhanced detection efficiency forthe remaining micro-beams. Such masking layers may be placed in front ofthe object to be examined, between the object and the detector, or bedesigned as part of the detector structure itself.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a schematic view of an x-ray imaging systemproviding an array of micro-beams as may be used in some embodiments ofthe invention.

FIG. 1B illustrates a cross-section view of the x-ray imaging system ofFIG. 1A.

FIG. 2 illustrates the use of a Talbot interference fringe pattern froma 1:1 duty cycle absorption grating G used as an array of micro-beamsfor an embodiment of the invention.

FIG. 3A illustrates a schematic view of the micro-beams, object, anddetector as used in some embodiments of the invention.

FIG. 3B illustrates a schematic cross-section view of the micro-beams,object, and detector of the embodiment of FIG. 3A.

FIG. 3C illustrates a schematic cross-section view of the micro-beams,object, and detector of the variation of the embodiment of FIGS. 3A and3B, in which portions of the detector array are active elements andother portions are inactive.

FIG. 4 illustrates a schematic view of a microscope system using abeam-splitting grating G₁ to generate micro-beams from Talbotinterference fringes.

FIG. 5 illustrates a cross section of a micro-beam intensity pattern asmay be formed using certain beam splitting gratings as used in someembodiments of the invention.

FIG. 6A illustrates a view of a pair of phase-shifting gratings as maybe used in some embodiments of the invention.

FIG. 6B illustrates the effective phase shifts that will be produced bythe pair of phase-shifting gratings of FIG. 6A.

FIG. 7 illustrates a view of a t phase shifting grating as may be usedin some embodiments of the invention.

FIG. 8 illustrates a schematic view of a microscope according to anembodiment of the invention having a mask placed in front of the objectunder examination.

FIG. 9A illustrates a schematic view of the micro-beams, object, anddetector of the embodiment of FIG. 8.

FIG. 9B illustrates a schematic cross-section view of the micro-beams,object, and detector of the embodiment of FIG. 8.

FIG. 10 illustrates a schematic cross-section view of the micro-beams,object, and detector of an embodiment comprising a scintillatordetector.

FIG. 11 illustrates a schematic cross-section view of the micro-beams,object, and detector of an embodiment comprising a scintillator and ascintillator imaging system.

FIG. 12 illustrates a schematic view of a microscope according to anembodiment of the invention having a mask placed between the objectunder examination and the detector.

FIG. 13A illustrates a schematic view of the micro-beams, object, anddetector of the embodiment of FIG. 12.

FIG. 13B illustrates a schematic cross-section view of the micro-beams,object, and detector of the embodiment of FIG. 12.

FIG. 14 illustrates a schematic cross-section view of the micro-beams,object, and detector of an embodiment comprising a mask at the detectorand a scintillator.

FIG. 15 illustrates a schematic cross-section view of the micro-beams,object, and detector of an embodiment comprising a mask at the detectorand a scintillator and a scintillator imaging system.

FIG. 16 illustrates a schematic cross-section view of the micro-beams,object, and detectors for an embodiment comprising multiple detectors.

FIG. 17A presents a portion of the steps of a method for collectingmicroscopy data according to an embodiment of the invention.

FIG. 17B presents the continuation of the steps of the method of FIG.17A for collecting microscopy data according to an embodiment of theinvention.

Note: The illustrations in the Drawings disclosed in this Applicationare meant to illustrate the principle of the invention and its functiononly, and are not shown to scale. Please refer to the descriptions inthe text of the Specification for any specific details regarding thedimensions of the elements of the various embodiments (e.g. x-ray sourcedimension a, grating periods p₀, p₁, p₂, etc.) and relationships betweenthem.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

1. Imaging with Arrays of Micro-Beams.

FIG. 1A illustrates a simple embodiment of the invention comprising theformation of an array of micro-beams. An arrayed source 004 comprisingan electron emitter 011 that produces electrons 111 that bombard atarget 1000 comprising a region 1001 containing structures of x-raygenerating materials 704. In this illustration, four material structures704 that are sub-sources of the x-rays are shown arranged in an array,although the target may comprise any number of source points and, ofthese source points, any number may be used.

The four structures of x-ray generating materials 704, when bombarded byelectrons 111, produce x-rays 888 that propagate away from the target.In the embodiment as illustrated, these x-rays 888 enter an x-rayoptical system 3300 that converts the waveform into focused x-rays 888-Fthat form an image of the x-ray array region 1001 at a predeterminedregion 2001 in space. Such an optical system may be a simple x-rayfocusing element, such as a capillary with an inner quadric surface, ora more complex multi-element imaging system. In this case, with fourx-ray source points, the image will comprise four spots 282-F, eachhaving a diameter related to the size of the original x-ray generatingsource point and the magnification of the optical system 3300, andhaving a length defined by the depth-of-focus of the optical system,generally related to the x-ray wavelength and the square of thenumerical aperture (NA) of the x-ray optical system.

FIG. 1B illustrates a cross section view of the converging x-ray field888-F, showing the formation of micro-beams 888-M at this point inspace. By placing an object to be examined 240-W at this position inspace, the micro-beams 888-M will illuminate the object at specificspatially defined points 282-F, having a diameter of the micro-beam888-M, which is determined by the size of the original x-ray sourcepoint, the x-ray wavelength, and the properties (NA, Magnification) ofthe optical system 3300. By placing an x-ray detector 290 having pixels291 with a pitch matched to the pitch of the micro-beams 888-M and aposition within the depth-of-focus, the x-rays detected by each pixelare therefore provided by only one micro-beam. The entire signalgenerated therefore represents the x-ray transmission of only the muchsmaller illumination spot 282-F. As an example, for a micro-beamdiameter of 1 micron, a detector pixel as large as 25 microns mayprovide information about only the single micron diameter spot when thepitch between micro-beams is larger or equal to the detector pixelpitch.

Such a system will produce a set of arrayed points from the detectorrepresenting sample points at each micro-beam. For some applications,this sampling of the x-ray transmission through an object may besufficient. In other cases, the relative position of the object and thearray of micro-beams may be scanned in x- and y-dimensions to produce ascanned “map” of the object. Since each data point represents theinformation produced by a smaller micro-beam, a high-resolution imageusing a lower-resolution pixel detector can be achieved. Such scanningtechniques for structured illumination have been additionally describedin co-pending U.S. patent application Ser. No. 15/173,711 entitled X-RAYTECHNIQUES USING STRUCTURED ILLUMINATION, filed Jun. 5, 2016, and in theU.S. Provisional Patent Application 62/401,164 entitled X-RAYMEASUREMENT TECHNIQUES USING MULTIPLE MICRO-BEAMS, which are both herebyincorporated by reference in their entirety.

The above example presents one way to form an array of micro-beams usingan arrayed x-ray source and imaging optics. Although functional fordemonstrating the principle, such an approach is limited by the field ofview of the x-ray optical system, and various embodiments of theinvention may use any number of techniques that create an array ofmicro- or nano-scale x-ray beams used for illuminating an object.

2. Talbot Fringes as an Array of Micro-Beams.

Talbot interference fringes can be a highly efficient method ofdirecting x-rays into an effective array of micro-beams. The effectivelateral dimension of the Talbot anti-nodes (typically defined as regionsof constructive interference) can, using the appropriate beam-splittinggrating to establish the fringes, be made to be very small, as small as20 nm, while the overall interference field of the Talbot interferencepattern can cover an area of several cm². A Talbot interference pattern,when used to illuminate an object under investigation in transmission,provides an array of discrete micro- or nano-probes that can be detectedand analyzed using an array detector.

As was described above for the imaging system, when the detector isselected to have a pixel size that corresponds to the pitch of theTalbot fringes, and both the object and the detector are placed withinthe effective “depth-of-focus” of the Talbot fringes, each pixel isdetecting transmitted x-rays from a single one of the micro-beams. Thisallows the advantages of decoupling the illumination spot size and thepixel dimension to be achieved, and the Talbot interference phenomenonallows an array of effective micro-beams to be formed over a large area.

Talbot interference fringes using a structured x-ray source have beenthe subject of other Patent Applications by the inventors of the presentApplication, including Ser. Nos. U.S. Ser. No. 14/527,523, U.S. Ser.Nos. 14/700,137, 14/712,917, U.S. Ser. Nos. 14/943,445, and 15/173,711,all of which are hereby incorporated by reference.

Talbot interference has been used for lower resolution imaging, and inparticular, for phase contrast imaging, for some time (See, for example,Atsushi Momose, Wataru Yashiro, and Yoshihiro Takeda, “X-Ray PhaseImaging with Talbot Interferometry”, in Biomedical Mathematics:Promising Directions in Imaging, Therapy Planning, and Inverse Problems,Y. Censor, M. Jiang and G. Wang, Editors, (Medical Physics Publishing,Madison, Wis., 2009), pp. 281-320 and references therein). Such systemstypically use a diffractive grating (often a phase-shifting grating) toproduce the Talbot interference pattern, and then analyze the resultingpattern with a second grating and/or an array x-ray detector.

FIG. 2 illustrates a cross section of representative Talbot interferencepattern generated by an absorption grating G having a 50/50 duty cyclewith a pitchp when illuminated by a plane wave. The fringes in thisillustration are adapted from FIG. 19(a) of section 9.3, “Phase ContrastImaging”, in Elements of Modern X-ray Physics, Second Edition”, JensAls-Nielsen & Des McMorrow (John Wiley & Sons Ltd, Chichester, WestSussex, UK, 2011). This has been presented for illustrative purposesonly; no restriction or limitation of the scope of the invention shouldbe implied by the use of this particular illustration.

As shown in FIG. 2, interference fringes are generated behind theabsorption grating. Self-images of the grating with pitch p and a 50/50duty cycle occur at the Talbot distances D_(T), given by

$\begin{matrix}{D_{T} = {n\frac{2p^{2}}{\lambda}}} & \left\lbrack {{Eqn}.\mspace{11mu} 1} \right\rbrack\end{matrix}$where p is the period of the beam splitting grating, n is an integer,and λ is the x-ray wavelength. The darker regions, where destructiveinterference occurs, are generally called “nodes” of the interferencepattern, whereas the bright regions of constructive interference aregenerally called “anti-nodes” of the interference pattern.

As an x-ray illuminator, the Talbot interference pattern can, with thesuitable selection of a beam-splitting grating with micron-scalefeatures, produce an interference pattern of bright anti-nodes with acorresponding micron-scale for the anti-node dimension. For x-rays withan energy of 24.8 keV, the wavelength is λ=0.05 nm, so for an absorptiongrating with a 50/50 duty cycle and a 1 micron pitch, the first (n=1)Talbot distance is D_(T)=4 cm. Therefore, the scales for the x- andy-directions of the fringes in the illustration of FIG. 2 are quitedifferent, with micron-scale dimensions perpendicular to the directionof propagation shown, but centimeter-scale dimensions used along thedirection of propagation.

Fringe patterns at various fractional Talbot distances may be invertedin bright and dark fringes, and the size of the bright (anti-node)fringes at various fractional Talbot distances may actually be smallerthan the size of the original grating features. These anti-nodes maytherefore serve as the multiple micro-beams used for illuminating anobject.

When Talbot interference phenomena is utilized, there are specificpredetermined regions within the Talbot interference pattern over whicha bright fringe maintains a certain intensity micro-beam profile. Suchregions (several of which can be seen in the example of FIG. 2) arecomparable to the “depth-of-focus” range of more conventional imagingsystems, and for a Talbot pattern arranged as an array, thesecorresponding predetermined regions will form an array of micro-beams.The region of the “depth-of-focus” may be also defined relative to theTalbot Distance D_(T). For example, in the illustration of FIG. 2, aregion of an anti-node forming a micro-beam is illustrated as having alength of approximately 1/16 D_(T). Placing the object 240-W and thedetector 290 having a pixel 291 within this predetermined anti-noderegion allows the signal from a much larger pixel 291 to represent thetransmission of the much smaller region 282 where the anti-nodeilluminates the object.

The pattern shown in FIG. 2 represents a non-divergent Talbotinterference pattern, but in some embodiments, the Talbot pattern willbe comprise x-rays which are diverging from a common x-ray source.

In many embodiments, the beam splitting diffraction grating used to formthe Talbot pattern may be a phase grating of low absorption butproducing considerable x-ray phase shift of either π/2 or π radians, orsome other specified or predetermined value such as an integer multipleof π/2. These gratings may also comprise one-dimensional ortwo-dimensional grating patterns.

As noted above, depending on the dimensions of the beam-splittinggrating, these probe sizes can be as small as 20 nm with the appropriateselection of a suitably fine beam-splitting grating. As in thepreviously mentioned co-pending US Patent Applications and USProvisional Patent Applications, scanning the object in x- andy-dimensions allows the micro- or nano-scale probing beams to be movedover the object so that a complete high resolution “map” of thetransmission of the object may be obtained with a relatively lowerresolution detector.

A schematic of an embodiment as may be used with any micro-beam formingsystem is illustrated in FIGS. 3A and 3B. When an array of micro beams888-M having a pitch p_(w) is formed, the object 240 to be examined isilluminated at an array of discrete interaction locations 282 alsohaving pitch p_(w). As illustrated, the x-ray beam pitch in x- and y- isthe same and equal to p_(w), but other embodiments in which the pitch inx- and y-dimensions are different may also be used. Differences in pitchmay also be due to divergence properties of the Talbot pattern. FIG. 3Cillustrates the use of a detector 290-A, in which active pixels 291-Pand inactive areas 291-A are both present in the detector to select onlycertain micro-beams for detection.

The position of the object can be scanned in x- and y-dimensionsperpendicular to the direction of propagation of the micro-beams using aposition controller 245, and the transmitted x-rays 888-T resulting fromthe interaction of the micro-beams and the object can be detected by anarray detector 290.

In this embodiment, the array detector 290 has a pitch p₃ which, in thisexample, is also equal to p_(w). This means that the detector will bealigned such that each pixel of the array detector will be positioned tocollect only x-rays corresponding to a single micro-beam. By pairing theuse of multiple micro-beams with a detector having a pixel pitch matchedto the pitch of the micro-beams, and also aligned so that each pixeldetects x-rays from only the interaction of a single micro-beam at agiven position on the object, the equivalent of 10² to 10⁴ parallelmicro-beam detection systems can be created. Other detectors withsmaller pixels, in which multiple pixels detect the x-rays of a singlemicro-beam, may also be used, as long as all transmission x-raysdetected by each pixel have their origin from a single micro-beam.

As before, the object can then be scanned in x- and y-coordinates. Thisproduces “maps” in parallel of the properties of the object, but therange of motion can be reduced to only correspond to the pitch of themicro-beams (although some overlap between scanned areas may beappropriate to provide a relative calibration).

The “maps” generated by each pixel may then be stitched togetherdigitally to produce a large-scale “macro-map” of the object properties,while reducing the corresponding data collection time by a factorrelated to the number of micro-beams (e.g. up to a factor of 10⁴).

To achieve some degree of tomographic analysis, limited angle adjustmentof the object may also be added to the motion protocol, as long as theinteraction of x-rays with the region of interest in the object as wellas the corresponding detector pixel both remain within a region definedby the depth-of-focus for all of the multiple micro-beams. A rotationstage 248 to achieve this purpose has also been illustrated as part ofthe mount for the object 240 in FIG. 3A. In some embodiments, a 5-axismount, or a goniometer, may be used to allow translation and rotationfrom the same mounting system. In some embodiments, the object mayremain stationary, and mechanism forming the Talbot fringes (along withthe aligned detector) may be translated or rotated relative to theobject.

Although the periodic Talbot pattern may be formed by any of the meansas described in the previously cited references and Patent Applications,one innovation that has been shown to enable greater x-ray power employsan x-ray source patterned according to a periodic pattern A₀. FIG. 4illustrates an embodiment having the configuration shown in FIGS. 3A and3B, but in which the x-ray micro-beam array 888-M is formed using such aperiodic x-ray source to generate a Talbot interference pattern.

In this configuration as illustrated, the x-ray source 002 comprises anelectron beam 111 bombarding an x-ray target 100 comprising a region1001 comprising structures 700 comprising x-ray generating materialembedded in a substrate 1000. The structures 700 as shown are uniformelements of size a arranged in a periodic 2-D pattern with period p₀.When bombarded with electrons 111, these produce x-rays 888 in aperiodic pattern with period p₀.

The structures 700 comprising x-ray generating material may comprise aplurality of discrete finer microstructures. The x-ray generatingstructures may typically be arranged in a periodic pattern in one or twodimensions. X-ray sources using such structured targets are describedmore fully in the U.S. Patent Applications X-RAY SOURCES USING LINEARACCUMULATION (U.S. patent application Ser. No. 14/490,672 filed Sep. 19,2014, now issued as U.S. Pat. No. 9,390,881), X-RAY SOURCES USING LINEARACCUMULATION (U.S. patent application Ser. No. 14/999,147, filed Apr. 1,2016), and DIVERGING X-RAY SOURCES USING LINEAR ACCUMULATION (U.S.patent application Ser. No. 15/166,274 filed May 27, 2016), all of whichare hereby incorporated by reference in their entirety, along with anyprovisional Applications to which these Patents and co-pending PatentApplications claim benefit.

Also shown in FIG. 4 are elements typical for x-ray sources: the highvoltage source 010 that provides an accelerating voltage between theelectron beam emitter 011 and the target 100 through electrical leads021 and 022. The detector 290 is shown as having an array G_(D) with aperiod p₃ equal to p_(w), so that each micro-beam is actually uniquelydetected by one detector pixel. However, as discussed above, thedetector 290 is aligned such that each detector pixel corresponds tox-rays from only a single micro-beam. To facilitate this, the detectormay additionally have a positioning controller 255 to align the detectorpixels with the individual micro-beams.

The x-rays 888 that emerge from the arrayed source as an array ofindividually spatially coherent but mutually incoherent sub-sources ofillumination for the beam splitting grating G₁ 210-2D placed at adistance L from the arrayed x-ray source A₀. The position of the object240 to be illuminated by the array of micro-beams having a pitch p_(w)is placed at a further distance D from the beam-splitting grating G₁210-2D. To ensure that each x-ray sub-source in A₀ contributesconstructively to the image-formation process, the geometry of thearrangement should satisfy the conditions:

$\begin{matrix}{p_{w} = {{q\; p_{0}\frac{D}{L}} = {q\frac{p_{1}\left( {D + L} \right)}{L}}}} & \left\lbrack {{Eqn}.\mspace{11mu} 2} \right\rbrack\end{matrix}$where q=1 for a π/2 grating and q=0.5 for a π grating.

This configuration is called the Talbot-Lau interferometer [see FranzPfeiffer et al., “Phase retrieval and differential phase-contrastimaging with low-brilliance X-ray sources”, Nature Physics vol. 2, pp.258-261, 2006; and also Described in U.S. Pat. No. 7,889,838 byChristian David, Franz Pfeiffer and Timm Weitkamp, issued Feb. 15,2011], and has been previously demonstrated using a uniform x-ray sourceand a masking pattern to create the x-ray source array.

It should be noted that the arrayed x-ray source may also be provided insome embodiments using a uniform x-ray material and a masked gratingthat allows x-rays to emerge only from specific points arranged in anarray of dimension a and period p₀. The arrayed x-ray source disclosedabove, however, may have considerable advantages over such prior artsystems, as the use of discrete sources allows all generated x-rays tocontribute to the image forming process. An arrayed x-ray source mayalso be provided by selective bombardment of an x-ray generatingmaterial using a patterned electron beam. Such sources have beendescribed in more detail in the previously cited U.S. PatentApplications, incorporated by reference herein.

The x-ray energy spectrum of the micro-beams may be limited by the useof x-ray filters (or other means known to those in the art) to limit thex-ray bandwidth. The system of FIG. 4 is shown using such a filter 388to filter the x-rays 888 produced by the x-ray source 002 before theyencounter the beam splitting grating 210-2D. This may allow betterinterference contrast to be achieved. For some embodiments, having theaverage x-ray energy E₀ be between 5 keV and 100 keV, and using an x-rayfilter to produce an energy bandwidth of E₀±10% or E₀±15%, may bedesired. The contrast between regions of greatest intensity (generallythe center of the micro-beams) and the darkest intensity (generallyexactly between micro-beams) is preferred to be at least 50%, butsignals obtained with a contrast of more than 20%, even 10% in somecases, may be acceptable.

FIG. 5 illustrates a simulated example of a portion of a two-dimensionalx-ray intensity pattern that may be created using Talbot interferencefringes. If the beam-splitting grating has matching periods in x- andy-dimensions, a pattern such as that shown in FIG. 5 can be replicatedat the various “depths of focus” regions of the Talbot fringes.

The beam-splitting grating may be any number of phase-shifting patternsor, in some embodiments, be formed using a pair of gratings. Typicalcombinations of phase shifters may use 0, π/2, or π radian phase shiftsin various regions of the grating. Combinations of 1-D patterns or 2-Dpatterns may also be used.

In some embodiments, it may be easier to fabricate two 1-D gratings, andmount them orthogonally to each other to create a more complex 2-Dpattern. For these embodiments, the grating G₁ shown in FIG. 4 may bereplaced with a pair of gratings G_(A) and G_(B) mounted together. TableI shows the various transmission values and phase shifts that may beused for such a combination of 50/50 duty cycle gratings. The values fort and ϕ represent the transmission and phase shifts, respectively, fortwo portions of each grating. A grating portion with t=0 represents anabsorption transmission grating, and the phase shift of the opaquesection is irrelevant.

TABLE I Two 1-D 50/50 Crossed Grating Configurations Option 1 2 3 4 5 6G_(A) t = 1, 1 t = 1, 1 t = 1, 1 t = 1, 1 t = 1, 1 t = 0, 1 ϕ = 0, π/2 ϕ= 0, π ϕ = 0, π ϕ = 0, π ϕ = 0, π/2 ϕ = −, 0 G_(B) t = 1, 1 t = 1, 1 t =1, 1 t = 0, 1 t = 0, 1 t = 0, 1 ϕ = 0, π/2 ϕ = 0, π ϕ = 0, π/2 ϕ = −, 0ϕ = −, 0 ϕ = −, 0

A pair of gratings for Option 1 (two crossed t/2 phase shiftinggratings), in which the pitch p_(a) for G_(A) is the same as p_(b) forG_(B), is shown in FIG. 6A, and the result of the crossed gratings isshown in FIG. 6B. Such a pair of crossed gratings used as the phaseshifting grating in the embodiment of FIG. 4 will form an anti-nodepattern in the shape of the pattern shown in FIG. 5, withp_(x)=p_(y)=p_(a)=p_(b). Other options using π phase shifts can produceTalbot patterns having a pitch at ½ the pitch of the π/2 phase shiftinggratings.

Some of these configurations may also be fabricated using a singlegrating. For example, the crossed π phase shifting gratings of Option 2form a single checkerboard pattern having phase shifts of 0, π, and2π=0, which will produce the same phase shifts as the single π phaseshift checkerboard grating shown in the illustration of FIG. 7. This tooshould form a Talbot interference intensity pattern as was shown in FIG.5. Likewise, other 1-D or 2-D periodic patterns of π or π/2 phase-shiftsand/or absorption gratings, as described in the previously mentionedpatent applications and the other Talbot references mentioned in thisApplication, may also be used.

To ensure that the object 240 to be examined is illuminated by aperiodic pattern of x-ray micro-beams 888-M, the distance D between thegrating and the object should correspond to one of the fractional Talbotdistances, i.e.

$\begin{matrix}{D = {n\frac{p_{1}^{2}}{8\lambda}}} & \left\lbrack {{Eqn}.\mspace{11mu} 3} \right\rbrack\end{matrix}$where n is a non-zero integer. The suitable value of n may be differentif the grating is an absorption grating, a π phase-shifting grating, ora π/2 phase-shifting grating.

For more general situations, in which diverging/magnifying fringes, maybe used, this distance may be generalized to

$\begin{matrix}{D = \frac{\left( {n/8} \right)p_{1}^{2}L}{\left( {{\lambda\; L} - {\left( {n/8} \right)p_{1}^{2}}} \right)}} & \left\lbrack {{Eqn}.\mspace{11mu} 4} \right\rbrack\end{matrix}$

Another equation often used in Talbot-Lau systems relates the pitch p₁of the Talbot grating G₁ to the size a of the x-ray generating elementsin the arrayed source:

$\begin{matrix}{p_{1} \geq {L\frac{\lambda}{a}}} & \left\lbrack {{Eqn}.\mspace{11mu} 5} \right\rbrack\end{matrix}$Most embodiments of the invention employ a interferometric system inwhich the conditions presented in Eqns. 2-5 are met.

It should be noted that these embodiments as illustrated are not toscale, as the divergence, collimation, or convergence of the Talbotinterference pattern will depend on factors such as the x-ray energy, onhow well collimated the x-ray beam is and how far the object is placedfrom the source.

3. Detector Considerations.

As disclosed here, the detector pitch will be matched to the pitch ofthe multiple Talbot fringes so that each pixel is positioned to onlydetect x-rays emerging from the interaction of the object with a singlemicro-beam, and the cross-talk between pixels due to neighboringmicro-beams is minimized. Then, the data collection and finalreconstruction of the “map” of the properties of the object may proceed,knowing that the distinct signals from each pixel need not be furtherdeconvolved.

If there is cross-talk between micro-beams and pixels (e.g. due toscattering or fluorescence), additional image analysis may be able toremove some of the cross-talk if it can be properly calibrated. Energyresolving array detectors may also be used to separate signals fromtransmitted x-rays, refracted x-rays, scattered x-rays, and fluorescencex-rays.

This matching is most straightforwardly achieved if the detector pitchis a 1:1 match to the pitch of the micro-beams, i.e. each beam has acorresponding single pixel in the detector, and the detector is placedin proximity to the object and the micro-beams.

3.1 Finer Detector Pitch.

In some embodiments, detector pitches that are integer fractions of thepitch of the micro-beams (e.g. a 3× reduction in pitch, which wouldindicate 9 pixels are present to detect the x-rays corresponding to eachmicro-beam) may also be used. This may offer some advantages if thex-rays being detected have some spatial structure, for example if thedesired x-ray signal is related to small-angle scattering from theobject. Then, certain pixels of the detector can be aligned to detectonly the scattered x-rays, while the non-scattered beam may be collectedby a different pixel, or simply blocked by a blocked pixel.

3.2. Larger Detector Pitch.

In other embodiments, a detector pixel that is larger than the pitch ofthe micro-beam may be used. The detector may therefore be lessexpensive, and yet still produce a “high resolution” signal (since thespatial resolution is determined by the interaction volume of the Talbotfringe and the object, not the detector pixel size).

One disadvantage of this technique is that only 1 out of 4 micro-beamsis used for detection, and the other micro-beams are blocked. With alarger pixel, greater detection efficiency may be achieved for themicro-beams that are detected.

FIGS. 8-15 illustrate the use of larger pixels in some embodiments ofthe invention. FIG. 8 illustrates a schematic of an embodiment of asystem similar to that of FIG. 4, but in which a mask 270 with a numberof apertures 272 has been placed in front of the object 240 to block acertain number of micro-beams. As illustrated, 3 out of every 4micro-beams are blocked, with only 1 beam out of each 4 beams proceedingto illuminate the object and then be detected by the detector. Thismeans that if the pitch of the x-ray beams at the mask is p_(w), thepitch of the beams illuminating the object is 2p_(w). The detector pitchp_(D) may therefore be set to be equal to 2p_(w) as well, larger thanwas used for the configuration in FIG. 4. As illustrated, 3 of 4 beamsare blocked, but any number of beams may be blocked according to anynumber of predetermined patterns for various applications.

FIGS. 9A and 9B illustrate such an embodiment in more detail, presentingillustrations similar to those of FIGS. 3A and 3B. As can be seen by thecomparison with FIGS. 3A and 3B, because only a certain number ofmicro-beams are used, the pitch of beams at the detector issubstantially larger, and a less expensive detector 290-L with a largerpixel size may be used.

As illustrated up to this point, the x-ray detector is presented as adirect array detector, generating an electrical signal in response tothe absorption of x-rays. Some embodiments may use direct flat paneldetectors (FPDs) such as the Safire FPD of Shimadzu Corp. of Kyoto,Japan. Some embodiments may use complementary metal-oxide semiconductor(CMOS) imagers. Some embodiments may use energy resolving arraydetectors.

In other embodiments, the detector may use scintillators that emitvisible or ultraviolet light when exposed to x-rays. The active x-raydetection region (the detector sensors) may be defined, for example, byproviding a scintillator such as cesium iodide doped with thallium (CsI:Tl) or by providing a detector with a uniform coating of scintillatorwith a masking layer of high Z material, for example, gold (Au), on top.

FIG. 10 illustrates a variation of the embodiment of FIG. 9B, but usinga detector 290-S in combination with a fluorescent screen orscintillator 280. The scintillator 280 comprises a material that emitsvisible and/or UV photons when x-rays are absorbed, and the detector290-S detects those visible and/or UV photons. Typical scintillatormaterials comprise a layer of thallium doped CsI, Eu doped LutetiumOxide (Lu₂O₃: Eu), yttrium aluminum garnet (YAG), or gadoliniumsulfoxylate (GOS).

The scintillator efficiency depends upon the fraction of x-rays absorbedby the scintillator and the amount of light produced by thescintillator. For high resolution, the lateral spread of light withinthe scintillator should be minimized and this often necessitates use ofa thin scintillator which may limit x-ray absorption and hence detectionefficiency.

In conventional imaging systems, high resolution images with ascintillator-type detector in close proximity to the object can beobtained, but the overall thickness of the scintillator and electronicelements must be thin enough so that each detector pixel is collectingonly x-rays corresponding to that pixel. This may also dictate the useof a thinner scintillator, reducing the ultimate sensitivity.

However, in the embodiments disclosed in this Application, the spatialresolution is defined by the dimensions of the micro-beams 888-M insteadof the detector pixel size. This allows a larger pixel and thereby athicker scintillator material with higher efficiency to be used, sinceevery photon generated from the larger pixel will be known to haveoriginated from a predetermined micro-beam.

FIG. 11 illustrates an additional variation on a system using ascintillator, in which the visible/UV light 890 from the scintillator280 is collected by a visible/UV optical system 320 and imaged onto adetector 290-SI. The visible/UV optical system may comprise optics withadditionally magnify the image of the scintillator. When using relayoptics and a magnified image, the electronic detector need not comprisea high resolution sensor itself, and less expensive commercial CCDdetectors or complementary metal-oxide-semiconductor (CMOS) sensorarrays with, for example, 1024×1024 pixels, each 24 μm×24 μm square, maybe used.

Thicker scintillators may also be used in some embodiments having relayoptics, increasing sensitivity. However, when relay optics are used,detection is limited to the field of view collected by the x-ray optics,which may in some cases be only on the order of hundreds of microns.Collecting data on larger areas can only be accomplished if images are“stitched” together from several exposures.

FIGS. 12, 13A and 13B represent an additional embodiment in which amasking structure 297 with apertures 292 is placed between the object240 and the detector 290-M. For this embodiment, all availablemicro-beams 888-M illuminate the object 240, but a masking layer 297made of, for example, gold (Au), prevents 3 out of every 4 beams fromentering the detector 290-M. This also allows detector 290-M to have alarger pixel, again reducing cost for direct detectors and, forembodiments using scintillators, increasing potential detectorefficiency.

FIG. 14 illustrates an additional variation of the embodiment of FIGS.10, 11A and 11B, but with the detection of x-rays achieved using athicker scintillator 280-S and a visible/UV light detector 290-S.

FIG. 15 illustrates an additional variation on a system using ascintillator, in which the visible/UV light 890 from the scintillator280 is collected by a visible/UV optical system 320 and imaged onto adetector 290-SI.

Commercial flat panel digital x-ray sensors in which a layer ofscintillator material is placed in close proximity to (or even coatedonto) an array of conventional optical image sensors are manufacturedby, for example, Varian Inc. of Palo Alto, Calif. and General Electric,Inc. of Billerica, Mass. Other configurations of image sensors may beknown to those skilled in the art.

Although the scintillators as illustrated in FIGS. 10, 11, 14, and 15are shown as comprising uniform layers of scintillator, embodimentsusing patterned scintillator material, in which scintillator material isplaced only over a portion of the pixel, may also be used. The selectiveplacement of scintillator material over portions of the detector may beused as an alternative to the use of a masking layer to select certainmicro-beams for detection.

Detectors with additional structure within each pixel may also beemployed as well. For example, if the typical detector pixel is 2.5microns by 2.5 microns (an area of 6.25 micron), but the micro-beamdiameter is only 1 micron, a detector pixel with a central “spot” ofscintillator material slightly larger than 1 micron and positioned tocorrespond to the position of the micro-beam may be created. With thisconfiguration, all the x-rays from the micro-beam should be detected,while reducing the detection of scattered or diffracted x-rays thatwould otherwise cause spurious signals if the full area of the detectorpixel were to be used.

Likewise, pixels in which detector structures (such as scintillatormaterial) are only positioned on the outer portion of the pixel, forexample, to only detect x-rays scattered at small angles while notdetecting the directly transmitted beam, may also be used for someembodiments.

Similarly, although the mask 297 in FIGS. 13 and 14 is shown asdisplaced from the scintillator 280, some embodiments may have the mask297 directly deposited onto the scintillator 280. Other embodiments forpatterned scintillators may be known to those skilled in the art.

3.3. Detector Variations.

The descriptions above disclose embodiments in which certain portions ofthe detector are not used for detecting x-rays by using a masking layerto block some number of micro-beams. Similar masking effects may beachieved for some configurations by using an array detector in whichcertain pixels are simply made inactive, either by removing power fromthe inactive pixels, so they do not produce a signal, or by usinganalysis software that ignores or eliminates any signals being generatedby the “inactive” pixels. These “inactive” pixels serve the samefunction as the space between pixels 291-A, as was illustrated in FIG.3C.

These inactive regions may also be regions transparent to x-rays,allowing the use in some embodiments of multiple detectors. In suchembodiments, each detector is positioned to detect only a selectednumber of the x-ray beams. This may be done by using a detector withpixels designed to detect only a predetermined number of the beams,while allowing other beams to pass through the detector.

Such a configuration is illustrated in FIG. 16. The first detector 290-1is an array detector with a pixel sized to detect all the transmittedx-rays corresponding to a single micro-beam, transmissive regionsbetween the pixels. Micro-beams incident upon these transmissive regionsthen pass through the detector 290-1, and fall onto a second detector290-2 with pixels aligned to detect these alternative x-ray micro-beams.

In some embodiments, the first detector 290-1 may be transmissive overthe entire region to high energy x-rays and the first detector 290-1 isused to detect the lower energy x-rays while the second detector 290-2is used to detect higher energy x-rays. Such a configuration may includetwo, three, or more detectors, depending on how many pixels areactivated in the first detector and how many micro-beams are allowed topass through the first detector to be detected or pass through thesecond detector. The advantage of this approach over the maskingapproach is that each x-ray micro-beam is eventually detected and cancontribute to the final collected data set.

4.0 Methods of Microscopic Data Gathering.

The process steps to form an image using micro-beams according to anembodiment are represented in FIGS. 17A and 17B, and are describedbelow.

In the first step 4210, a region of space in which the object will beexamined by an array of micro-beams is determined. This region may be aregion bounded by the “depth of focus” discussed above for themicro-beams, or may be defined as a region related to a fraction of theTalbot distance D_(T) for a given Talbot pattern, or by any criteriasuitable to the measurements desired.

In step 4220, an array of micro-beams having a pitch p is formed in thepredetermined region. Such micro-beams may be formed by any of thedisclosed methods, including by using an x-ray imaging system or byusing Talbot interference phenomena. In some embodiments, such as whenthe interference field is formed by a Talbot interference pattern, thisregion may be defined as a region with a length related to a fractionalTalbot distance, e.g. ⅛ D_(T) or 1/16 D_(T).

The micro-beams within this region may have a lateral pattern in theform of an array of circular beams or beams with a square or rectangularprofile. The array of micro-beams will generally be propagating in asingle direction (generally designated the “z” direction), with a pitchp between micro-beams in the directions orthogonal to the propagationdirection (the “x” and “y” directions) being 20-50 micrometers or less.

In some embodiments, this step may also be used to insert an additionalmask that removes some of the micro-beams, as discussed above.

Once the micro-beam region has been established, the next step 4230 isthe placement of a detector having a pixel pitch p_(d) equal to anon-zero integer multiple of the micro-beam pitch p. The detector may beany of the detectors as described above. This sensor portion of thedetector is placed in the region selected in the previous step. There issome flexibility in the exact positioning of the detector, as long aseach pixel of the detector generates a signal corresponding only to asingle micro-beam (without cross-talk between the micro-beams ordetector pixels). Generally, a detector will be chosen where everymicro-beam has a corresponding pixel or set of pixels; however, in someembodiments, the detector may only detect a subset of the correspondingmicro-beams.

In the next step 4240, a region of interest (ROI) of an object to beexamined is placed in the selected region comprising micro-beams aswell, between the x-ray source and the front of the detector. This willgenerally be in proximity to the detector, so that the object anddetector are both within a “depth-of-focus” region of the micro-beam.Typically, the x-ray beam will either be blocked or turned off while theobject is positioned and aligned, and the x-rays turned on after theobject has been placed.

In the next step 4250, the x-rays transmitted by each micro-beam aredetected by the corresponding pixels on the detector, and thecorresponding electronic signals are recorded. These signals mayrepresent x-ray intensity in counting detectors and may also includeenergy in energy-resolving detectors.

In the next step 4256, a decision on how to proceed is made. If only asingle set of datapoints are desired, no more data need be collected,and the method proceeds to the step indicated by “B” in FIGS. 17A and17B. If, on the other hand, additional data need to be collected tobuild up a 1-D or 2-D “map” of the properties of the object, thedecision tree delivers a request for data from additional positions.

In the next step 4260, the relative position of the object and themicro-beams is changed by a predetermined distance in x- and/ory-dimensions, and the method reverts to step 4250, in which data is nowcollected for the new position. The system will loop through thisdecision tree of steps 4250, 4256, and 4260 until data have beencollected for the entire 1-D or 2-D region designated for examination,at which point the method proceeds to the step indicated by “B” in FIGS.17A and 17B.

Once one set of 2-D scanning data has been collected, the system willdetermine in steps 4266 and 4276 whether only a 2-D “map” is to beconstructed, or if additional information is needed to generate a 3-Drepresentation of the object, using algorithms related to eitherlaminography or tomography.

If no information beyond what has been acquired is needed, the methodproceeds to the final analysis step 4290. If data for a 1D or 2D map wastaken in the previous steps, the accumulated data is then used withvarious image “stitching” techniques that are generally well known inthe art to synthesize a 1-D or 2-D intensity “map” representing thex-ray transmission/absorption of the ROI of the object.

If, on the other hand, 3-D information is desired, in the next step4276, a decision on how to proceed is made. If additional data is stillrequired to be collected to build up a 3-D dataset of the properties ofthe object, the decision tree delivers a request for data fromadditional angles.

The method then proceeds to a step 4280 in which the object is rotatedby a predetermined angular increment around an axis at a predeterminedangle relative to the z axis, and then the method proceeds to the stepindicated by “A” in FIGS. 17A and 17B, passing control back to the loopof steps 4250, 4256, and 4260 to collect a set of data from the x-raydetector at this alternative rotation position.

The system will loop through these steps 4250, 4256, 4260 and also 4266,4276, and 4280 to collect x-ray information at a preprogrammed sequenceof positions and rotations until a complete set of data is collected. Atthis point, after all data collection is complete, the system will thenproceed to the final analysis step 4290 to take the accumulated dataand, in this case, use various image 3-D analysis techniques that aregenerally well known in the art, to synthesize a 3-D representation ofthe x-ray transmission/absorption of the object ROI.

Variations on the method described above may also be put into practice.For example, instead of first executing a loop of data collection in x-and y-dimensions at a fixed rotation position, and then changing therotation setting to collect additional data, embodiments in which theobject is rotated while the x- and y-position settings remain fixed mayalso be executed. Rotation of the object around the z-axis may alsoprovide additional information that can be used in image tomosynthesis.

5. Limitations and Extensions.

With this Application, several embodiments of the invention, includingthe best mode contemplated by the inventors, have been disclosed. Itwill be recognized that, while specific embodiments may be presented,elements discussed in detail only for some embodiments may also beapplied to others. Also, details and various elements described as beingin the prior art may also be applied to various embodiments of theinvention.

While specific materials, designs, configurations and fabrication stepshave been set forth to describe this invention and the preferredembodiments, such descriptions are not intended to be limiting.Modifications and changes may be apparent to those skilled in the art,and it is intended that this invention be limited only by the scope ofthe appended claims.

We claim:
 1. A method of examining an object with x-rays, comprising:creating a periodic array of x-ray micro-beams propagating from a commonx-ray source, with each x-ray micro-beam at the object having an axisalong which the x-ray micro-beam propagates, and having a contrastbetween the x-ray intensity along the axis and the x-ray intensity at adistance equal to ½ of the period of said periodic array of x-raymicro-beams measured perpendicularly from said axis of greater than 10%;positioning an x-ray pixel array detector system comprising a pluralityof pixels so that each pixel detects x-rays corresponding to no morethan one x-ray micro-beam; illuminating a portion of said object withsaid periodic array of x-ray micro-beams; and recording signals producedby said x-ray pixel array detector system.
 2. The method of claim 1,wherein the periodic array of x-ray micro-beams is created throughTalbot interference phenomena that form a Talbot interference pattern;and said x-ray micro-beams correspond to an array of constructiveinterference portions of the Talbot interference pattern.
 3. The methodof claim 2, additionally comprising: positioning an absorbing maskingcomponent having periodic transmissive portions that transmit only apredetermined subset of the x-ray micro-beams; wherein the period ofsaid transmissive portions in both lateral directions is equal to theperiod of the Talbot interference pattern multiplied by a positiveinteger N; and aligning said absorbing masking component so that saidtransmissive portions are centered with every Nth x-ray micro-beam. 4.The method of claim 1, additionally comprising positioning placing anabsorbing masking component having transmissive portions to transmitonly a predetermined subset of the x-ray micro-beams.
 5. The method ofclaim 4, wherein the lateral dimensions of said transmissive portionsare less than ¾ of the period of the periodic array of the x-raymicro-beams.
 6. The method of claim 1, additionally comprisingpositioning the x-ray pixel array detector system so that two or morepixels detect x-rays corresponding to the same x-ray micro-beam.
 7. Themethod of claim 1, wherein the signals correspond to the transmission ofsaid x-ray micro-beams through the object.
 8. The method of claim 1,wherein the signals correspond to an interaction phenomenon of saidx-ray micro-beams with the object, said interaction phenomenon selectedfrom the group consisting of: absorption, refraction, x-rayfluorescence, and small angle scattering.
 9. The method of claim 1,wherein the x-ray pixel array detector system comprises a first x-raydetector having periodic x-ray active areas positioned to detect x-raysand to produce signals corresponding to said x-rays, the periodic x-rayactive areas separated by x-ray inactive areas that do not producesignals, with the period of said periodic x-ray active areas configuredto detect only a predetermined subset of the x-ray micro-beams.
 10. Themethod of claim 9, wherein the x-ray inactive areas transmit x-rays, andthe x-ray pixel array detector system additionally comprises a secondx-ray detector positioned to detect the x-rays transmitted through thefirst x-ray detector.
 11. The method of claim 1, wherein the period ofthe periodic array of x-ray micro-beams at the object is less than 50micrometers.
 12. The method of claim 1, wherein the length of each x-raymicro-beam along said axis at the object is greater than 1 millimeter.13. The method of claim 1, additionally comprising: laterally displacingrelative positions of the object and the periodic array of x-raymicro-beams in at least one direction perpendicular to the axis of oneof the x-ray micro-beams by one or more times; recording signalsproduced by said x-ray pixel array detector system after each lateraldisplacement has occurred; and generating a two-dimensional image usingsaid recorded signals.
 14. The method of claim 13, wherein laterallydisplacing the relative positions of the object and the periodic arrayof x-ray micro-beams is carried out by laterally displacing the object.15. The method of claim 1, additionally comprising: changing a relativeangular orientation of the object and the periodic array of x-raymicro-beams one or more times by an angle of 0.5 degrees or more;recording signals produced by said x-ray pixel array detector systemafter each change of the relative angular orientation has occurred; andgenerating a three-dimensional image using said recorded signals. 16.The method of claim 15, wherein changing the relative angularorientation of the object and the periodic array of x-ray micro-beams iscarried out by rotating the object.
 17. The method of claim 1, whereinsaid contrast is greater than 20%.
 18. The method of claim 1, whereinthe common x-ray source comprises an array of x-ray generatingmicrostructures.
 19. An x-ray microscope system comprising: a source ofa periodic array of x-ray beams configured to impinge at least a portionof an object to be examined; at least one x-ray pixel array detectorcomprising a plurality of pixels positioned to detect x-rays resultingfrom an interaction of said periodic array of x-ray beams with saidobject, the at least one x-ray pixel array detector producing at leastone signal corresponding to said detected x-rays, and with said at leastone x-ray pixel array detector aligned such that the x-rays detected byany single pixel of the plurality of pixels correspond to only one ofthe x-ray beams from among the periodic array of x-ray beams.
 20. Thex-ray microscope system of claim 19, wherein the source furthercomprises at least one x-ray filter configured to limit the bandwidth ofthe x-rays.
 21. The x-ray microscope system of claim 20, wherein the atleast one x-ray filter produces an x-ray spectrum having an averageenergy E₀ and an energy bandwidth within E₀±15%.
 22. The x-raymicroscope system of claim 19, wherein the source comprises a gratingstructure to generate a Talbot interference pattern; and wherein theperiodic array of x-ray beams corresponds to x-ray anti-nodes of theTalbot interference pattern and has a contrast between the Talbotanti-nodes and the neighboring Talbot nodes is greater than 10%.
 23. Thex-ray microscope system of claim 22, wherein the object to be examinedand the pixels of the x-ray pixel array detector are both positionedwithin a depth-of-focus of the Talbot interference pattern.
 24. Thex-ray microscope system of claim 22, further comprising a mountconfigured to translate said object in two orthogonal directions. 25.The x-ray microscope system of claim 22, wherein the grating structureto generate a Talbot interference pattern comprises one or more of: anabsorption grating, a π/2 phase shifting grating, an phase shiftinggrating, a 1-D array of grating structures, a 2-D array of gratingstructures, a grid structure, and a checkerboard phase gratingstructure.
 26. The x-ray microscope system of claim 22, wherein thedimensions of the grating structure are selected such that the period ofthe period of the Talbot interference pattern is less than 50micrometers.
 27. The x-ray microscope system of claim 19, additionallycomprising a mask positioned to block a predetermined number of thex-ray beams.
 28. The x-ray microscope system of claim 19, wherein thex-ray pixel array detector is an energy resolving pixel array detector.29. The x-ray microscope system of claim 19, additionally comprising adata collection and analysis system to analyze said at least one signal.30. The x-ray microscope system of claim 19, wherein the sourcecomprises: a vacuum chamber; an emitter for an electron beam; and anelectron target comprising: a substrate comprising a first material and,embedded in the substrate, at least a plurality of discrete structurescomprising a second material configured to generate x-rays in responseto electron bombardment.
 31. The method of claim 1, wherein recordingsignals produced by said x-ray pixel array detector system comprises:using a first detector of the x-ray pixel array detector system todetect x-rays from the object; transmitting x-rays from the objectthrough the first detector; and using a second detector to detect x-raystransmitted through the first detector.
 32. The x-ray microscope systemof claim 19, wherein the at least one x-ray pixel array detectorcomprises: a first x-ray pixel array detector comprising pixels andx-ray transmissive regions between the pixels; and a second x-ray pixelarray detector configured to detect x-rays transmitted through the x-raytransmissive regions of the first x-ray pixel array detector.